The invention is directed to improvements in a fuel injection pump for internal combustion engines, in particular an in-line injection pump for Diesel engines.
In a known fuel injection pump of this type (German Offenlegungsschrift No. 33 04 335), the fuel feed pump is embodied with a reversible direction of rotation, and an electrically controllable switching valve that is closed when without electric current is incorporated into the pressure line between the feed pump and the suction chamber. Additionally, the feed pump communicates on the pressure side with the suction chamber via a second switching valve that is closed when without electric current. The switching signal arising at the output of the emergency shutoff device if there is a malfunction in the injection quantity governor causes de-excitation of the first switching valve and the supplying of current to the second switching valve, so that the inlet to the suction chamber is blocked and the second connection between the suction chamber and the feed pump is opened up. The switching signal also causes a reversal of polarity of the feed pump drive, reversing the feed direction of the feed pump. Fuel is now aspirated from the suction chamber by the feed pump via the open second connection. Check valves in the pressure line to the suction chamber and in the intake line from the fuel tank as well as in the second connection to the suction chamber and in a further connection to the fuel tank assure that the fuel aspirated out of the suction chamber flows back into the fuel tank. Once the suction chamber is evacuated, the plunger of the fuel injection pump cannot feed any fuel during the intake stroke, and the engine stops.
The problem with this known pump is that providing the circuitry for the emergency shutoff of the engine in the event of malfunction of the injection quantity governor is relatively expensive in engineering time and effort.